Study On Antibacterial Performance Of ZnO Hierarchical Nanostructures For Implant Surface Modification

Background and Objective:Nowadays,titanium(Ti)and tantalum(Ta)have been extensively used as implants due to their excellent mechanical strength and moderate biocompatibility.The implant surgery is a traumatic surgery,postoperative complications are also more likely to occur,the most common is the infection.Postoperative infection affects the success of the operation,not only prolonging the patient's hospital stay,but also caused additional pain and burden.In particular,artificial joint replacement surgery,postoperative infection is disastrous,requiring secondary surgical treatment,will give patients a serious mental and financial burden.In particular for artificial joint replacement surgery,postoperative implant infection is commonly disastrous,requiring secondary surgical treatment,give patients a serious mental and financial burden.In addition to mechanical requirements,the surface performance of the implant is also very important,especially for long-term antibacterial properties.Unfortunately,in this aspect,neither the most commonly used Ti nor the emerging Ta possess significant antibacterial properties.Therefore,it is necessary to improve their antibacterial properties through appropriate surface modification,so as to effectively reduce the risk of implant-related infection.Methods:(1)The surface of titanium and tantalum was coated with ZnO nanorods arrays by a water bath method,drop on ZnO nanoslices,drying as ZnO nanorods-nanosli-ces hierarchical structure(NHS).Field-emission scanning electron microscopy(FE-SEM)was utilized to examine the surface topography of the specimens.The crystalline structure of the samples was determined by X-ray diffraction(XRD)and Transmission electron microscope(TEM);(2)After ultrasonic cleaning,the quality of ZnO on the surfaces of Ti and Ta was measured,the release of ZnO in the surface of Ti and Ta was observed by ICP for 2 weeks in deionized water;(3)Incubation with Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)in an incubator for 8h,24 h,and 48 h,demonstrated antimicrobial activity of different ZnO modified Ti and Ta in vitro;(4)Two weeks after co-culture with S.aureus in mouse back were carried out to investigate the antibacterial activity of Ti and Ta modified with different ZnO by muscle and skin section pathology in vivo;(5)The osteoblasts(MC3T3-E1 cells)were used to verify the biocompatibility of Ti and Ta after ZnO modification.Results:SEM can clearly observe the synthesis of ZnO NHS.The underlying layer was the ZnO nanorods;the top layer was the ZnO nanoslices,XRD further proves the result;(2)After ultrasound treatment,the ZnO nanoslices groups had highest mass alter from 7.3 ± 0.4 mg/L(Ti),7.33 ± 0.23 mg/L(Ta)to 0.43 ± 0.17 mg/L(Ti),0.33± 0.17 mg/L(Ta)(p< 0.01).The amounts of released Zn were 0.64 ± 0.1 mg/L(Ti)and 0.73 ± 0.11 mg/L(Ta)in the first two days,respectively and decrease quickly afterward.After 14 d,the releasing of zinc tended to be stable at 0.05 ± 0.02 mg/L.;(3)ZnO nanoslices(98 ± 1%)and ZnO NHS(99 ± 1.1%)had higher antibacterial rates in 8 hours for E.coli in Ti,compared to the ZnO nanorods(13.4 ±6.6%).after co-cultured with bacteria for one day,the antibacterial ratio of ZnO nanorods increased to 81.3 ± 6.2%,which was very close to the level of ZnO nanoslices(82.2 ± 9.3%)and ZnO NHS(87.4 ± 7.2%).On the other hand,after ultrasound treatment,the ZnO nanorods(98.2 ± 3.6%)and ZnO NHS(90.5 ± 5.9%)groups still maintain a high antibacterial property.For S.aureus,the resaults were similar.(< 0.01);(4)From the blank control groups(Ti or Ta),we can observed the normal nucleus in skin and muscle.The surroundings of ZnO nanoslices,ZnO nanorods,ZnO NHS implant materials,after soaked in a bacterial suspension of S.aureus,had a similar result.In contrary,the tissues around the naked implant materials,which were treated with S.aureus solution,exhibited high-density nucleus of inflammatory cells in both skin and muscle samples.(5)the osteoblast(MC3T3-E1 cells)was used to test the cytotoxicity of Ti or Tamodified with different ZnO.No obvious cytotoxicity was observed from ZnO nanoslices group,ZnO nanorods group and ZnO NHS group,compared to the Ti or Ta control group.(> 0.05)Conclusion:(1)ZnO NHS were constructed to modify the surface of Ti and Ta based implants,exhibited unique staged release characteristics for short-term quick release and long-term slow release,which integrated rapid steriliza-tion and long-lasting inhibition against both Gram-positive bacteria and Gram-negative bacteria;(2)ZnO NHS modified Ti or Ta implants have moderate biocompatibility,can significantly reduce the risk of bacterial-induced surgical infections in orthopedics,decrease the use of antibiotics and avoid the problems of antibiotic abuse..